Also, Java is extremely popular, and some of its most painful points have been addressed in Java 8. Even an arguably better language (regardless of its name) will not easily replace Java. Hey, look across the browser at JavaScript. There are arguably better languages there; are they replacing JavaScript?
If you look just at GitHub – which is greatly skewed towards new languages – you see that all other JVM languages put together make about 10% of the JVM ecosystem, with Java being the 90%. Outside of GitHub, in "the real world", the situation is even more strongly in favor of Java. I don't know if this is going to change much in the next few years.
I don't mean that you shouldn't use an alternative JVM language if it makes your work better, and there are many viable and very useful alternate JVM languages – personally, I like Clojure and Kotlin – but you can't just "replace" Java so easily. I think efforts to reform the Java ecosystem are more likely to succeed – at least in the short term – than efforts that require switching to a different JVM language.
I think it possible (though far from inevitable) that another JVM language will achieve dominance on the JVM, and it is very possible that Java will fall below the 60% or even 50% on the JVM (with the rest being taken by several, though not one dominant, languages). But this is still some years in the future.
It IS an improvement on/replacement for Java in most situations.
In short, no one (who knows the software development landscape well, that is) can say Scala (or some other JVM languages) makes Java redundant.
Maybe when some of these new fancy tools like Graal become more polished and ready the dream that was scala can start to happen vs reality you get when using it. I'd be happy to see that happen.
Frankly, I'd rather just go to Erlang and skip all the compromises needed to stay with the JVM if I want that kind of language.
I mean the most hated implicits are implicit conversions and they basically exist for Java compatibility.¹
So on the one side you have terrible stuff hard-coded into the language (Java, C#) which you will never get rid of and on the other side you have a solution as a library which you just can de-import if you don't want to suffer from e. g. magic anything-to-String conversions any longer (I certainly won't).
That's a huge plus in my book.
¹ The two other main use cases, type classes and extension methods, seem to be hugely popular and I haven't seen any criticism concerning them.